Inertia-type electromechanical sound transducing device



m 1950 E. H. GREIBACH 2,500,541

INERTIA-TYPE ELECTROMECHANICAL SOUND TRANSDUCING DEVICE Filed July 18, 1945 7 Sheets-Sheet 1 IN VEN TOR. E. H. GRE/BA CH A 7' TOPNEVS March 1950 E. H. GREIBACH 2,

INER'I'IA-TYPE ELECTROMECHANICAL SOUND TRANSDUCING DEVICE Filed July 18, 1945 7 Sheets-Sheet 2 INVENTOR. EH. GRE/BACH ATTORNEYS March 14, 1950 E. H. GRElBACH 2,500,541

INERTIA-TYPE ELECTROMECHANICAL SOUND TRANSDUCING DEVICE Filed July 18, 1945 7 Sheets-Sheet a 8m) b1 b2 i i I G1 1 c2 40 (G1) I 1 Z L-3 I V 21,22 :3) I- 5 (L- 2) 5o (c-a) RESPONSE IN DB zbo 660 who 20'00 5600 4060 5600 FREQUENCY IN CYCLES PER SECOND INVENTOR EH. GEE/EACH We 10 BY ATTORNEYS March 14, 1950 E. H. GREIBACH 2,500,541

INERTIA-TYPE ELECTROMECHANICAL scum) TRANSDUCING DEVICE Filed July 18, 1945 7 Sheets-Sheet 4 A TTORNEVS March 14, 1950 E. H. GREIBACHV 2,500,541

INERTIA-TYPE ELECTROMECHANICAL SOUND TRANSDUCING DEVICE Filed July 18, 1945 '7 Sheets-Sheet 5 INVENTOR. E. H. SRE/BA CH March 14, 1950 E. H. GREIBACH 2,500,541

INERTIA-TYPE ELECTROMECHANICAL SOUND TRANSDUCING DEVICE Filed July 18, 1945 7 Sheets-Sheet 6 IN V EN TOR. E. H. GRE/BACH BY mvw A 7 TORNEVS E. H. GREIBVACH 2,500,541 INERTIA-TYPE ELECTROMECHANICAL souND TRANSDUCING DEVICE March 14, 1950' Filed July 18, 1945 7 Sheets-Sheet 7 INVENTOR.

E. H. GRE/BACH ATTORNEVS Patented Mar. 14, 1950 UNITED STATES INERTIA-TYPE ELECTROMECHANICAL SOUND TRAN SDUCING DEVICE Emil H. Greibach, White Plains, N. Y. Application July 18, 1945, Serial No. 605,767

8 Claims.

This invention relates to electromechanical energy translating devices, and more particularly to electromechanical energy translating devices of the inertia reaction type, such as inertia reaction bone receivers described in my Patent Re. 21,030, or inertia reaction throat microphones described in my Patents 2,255,249 and 2,255,250.

In such devices, a vibratory contact portion, usually in the form of a completely closed casing which is held coupled to the body of the user, is connected through resilient junction elements to an additional mass portion so that the additional mass portion is resiliently carried in a vibratory condition by the contact portion; the additional mass portion constituting in conjunction with the mass of the contact portion and their interconnecting resilient junction elements parts of a magnetic core structure having a gap and Windings interlinked with the magnetic flux of the core so that oscillatory voltages impressed on the winding produce corresponding vibratory motion between the mass portions of the vibrating structure for inducing hearing by bone conduction-when the contact portion is held against the bones-and thatwhen the contact portion is held against the throat of a speaker-the resulting vibratory motion between the mass portions of the vibratory structure across said gap will induce corresponding voltages in the windings of the device for enabling intelligible reproduction of speech.

Among the Objects of the invention is a novel electromechanical energy translating device of the foregoing type which makes it possible to extend the frequency range of such devices without materially adding to their component parts or materially increasing their size.

The foregoing and other objects of the invention will be best understood from the following description of exemplifications thereof, reference being had to the accompanying drawings wherein Fig. 1 is a cross-sectional view of an electromechanical energy translating device exemplifying the invention, seen along line I-l of Fig. 2;

Fig. 1-A is an elevational view of the device of Fig. 1 used as a bone receiver;

Fig. 2 is a vertical cross-sectional view of the device of Fig. 1, along line 2-2 of Fig. 1, with the boundary of the casing indicated in dash lines;

Fig. 3 is a plan view of the inner vibrating structure of the device of Fig. I, seen from the bottom side;

Fig. 4 is a cross-sectional view similar to Fig. l with the internal vibrating unit shown in eleva- 4 tion;

Fig. 5 is a cross-sectional view similar to Fig. 4 without the internal vibrating unit;

Fig. 6 is a view similar to Fig. 3 with the bottom diaphragm member removed;

Fig. 7 is a plan view of the bottom diaphragm member of the device shown in Fig. 1;

Fig. 8 is a simplified diagrammatic view of the principal elements of the device shown in Fig. 1;

Fig. 9 is an electric analog of the device of Fig.

Fig. 10 is a curve diagram showing the response characteristics of the device of Fig, 1 when used as a throat microphone;

Fig. 11 is an electric analog of the device of Fig. 1 when operating with a damping resistance element;

Fig, 12 is a perspective view of an inner shell element of the device of Fig. 1;

Fig. 13 is a cross-sectional View of a modified form of a device of the type shown in Fig. 1

designed for operation with a throat micro-phone; Fig. 14 is a plan view of the bottom or outer diaphragm of the device of Fig. 13;

Fig. 15 is a cross-sectional view similar to Fig. 1 2c of the device of'Fig, 13, along line 15-45 of Fig, 16;

Fig. 16 is a cross-sectional view along line Iii-l6 of Fig. 13;

Fig. 17 is a plan view showing two throat microphone units of Figs, 13 and 15 joined in a double microphone unit;

Fig. 18 is a view similar to Fig. 12 of an inner shell for such microphone;

Fig. 18-A is a cross-sectional view of the shell of Fig. 18; and

Figs. 19 and 20 are cross-sectional views similar to Fig. 13 of two different modified forms of damping elements for such device.

In Figs. 1 to 7 is shown how the generally used commercial form of bone conduction receiver may be modified in accordance with the invention to operate with an extended frequency range. In the form shown, it comprises a small vibrating casing 2| having a detachable base 22 and em closing within its interior all the movable elements constituting with the casing an electromechanical energy translating device of the inreg'ionsof the armature.

vention, the casing forming the contact wall portion of the device. The base 22 is shown attached to the casing 2! by two screws 23, the

heads of which are confined Within recesses formed on the outer surface of the base wall 22, the screws engaging the internally threaded bushings 24 embedded in the end walls of the casing 2! which is made of a molded synthetic resin material of the type which gives the casing i the required degree of rigidity.

Within the casing is mounted an electromagnetic vibrating unit comprising. a magnetic core structure and an armature diaphragm 4! The magnetic core structure 36 comprises an oblong magnetic yoke or junction plate 3!, to the center of which is secured, as by a rivet connection, a cylindrical pole piece 3'2 which is sur- 7 rounded by operatin windings in the form of a coil 33. 34 are held clamped to the end regions of the oblong yoke 3! by a magnetic pole plate '35 of the same oblong shape which is shown secured to the yoke by two screws 36, the fiatheads of which are confined within recesses formed on the outer surface of the yoke plate. 'The pole plate has a central circular opening 31 separating its circularpole face region 35-4 from the circu- Two permanent magnet coreblocks 3 lar pole face region 32-! of the central pole 1 region 32! of the central pole piece 32 as well as an extensive area of the pole face 35! of j the surrounding pole plate 35 so thatthe armature shall provide a path for the closed magnetic of the outer pole plate, overlapped by the inter-- mediate armature portion 42 of the diaphragm, is substantially larger than the pole face area 32-! of the central pole'piece so that the principal magnetic forces exertedbetween the armature and the larger magnetic core structure are exerted only across the gap space separating the central pole face area 32-4 of the ,pole piece from the armature, thereby assuring that slight misalignment of the armature relatively to the magnetic structure of the pole pieces does not materially aifect the operating characteristics of the device. v

As shown in Figs. 1 to '6, the diaphragm armature is formed of a magnetic sheet member of substantial thickness which is shaped somewhat like an 8. Notwithstanding the small overall dimensions of the diaphragm armature 4!] and its substantial thicknesait is given the desired limited stiffnessdetermined by theresonant frequency at which it has to operate in the device-by joining each of the diaphragm end arms 4! to a region of the armature facing the other end arm through an intermediate arm section 43 extending on the opposite sides of the elongated armature portion lzfrom'the end Theend'portionsof the two end arms 4! of surface of the armature 42.

the armature diaphragm are shown afiixed to the pole plate by two screws M. Two stop screws 55 having heads-overlying intermediate portions of the diaphragm armature arms 4!, 43 and shanks extending through the slots i6 separating the diaphragm arms from the armature into engagement with threaded holes formed in the pole plateare so adjusted that the heads of the stop screws limit the maximum deformation that can be imparted to a diaphragm arm so that the strain to which it is subjected remains within the elastic limits of Hookes law.

As shown in Figs. 1, 2 and6, two set screws 4'! extending through threaded holes in a part of each diaphragm arm 4! near the clamping end thereof which is affixed to the pole plate '35 by screws 44, make it possible to adjustably set in a simpl manner the small gap spacing of the order of afew mils which has to be maintained between the pole faces and the facing The elements of the magnetic vibrating structure thus far described are identical with those employed in the now generally used small bone conduction receivers.

In accordance withthe invention, the armature ofsuch vibrating unit is joined to the contact wall structure through an additional vibratory diaphragm memb'ensuchas shown at '50, of a stiffness much greater than the stiiiness of the diaphragm member of such vibratory unit, so as to extend the frequency range over which suchdevice operateslwith ahigh efiiciency, without materially adding to the componentparts of such device or materially increasin the size of the device.

As indicated in Fig. 7, the additional diaphragm 50 shown is madeoiia flat, relatively thin, sheet stock of elastic spring metal. Itscentral portion 52 is secured to the central armature portion -42 of the armaturediaphragm 49 either byspot welding or by two screws '53, as shown, across an additional spacer and mass element M.

The central portion'52 of the additional diaphragm 5!], which is secured to the magnetic armature-'42, forms'with itand-the spacer mass element 54 a substantially rigid mass element joining the two diaphragm-s 451 and 5t, and is surrounded by a continuousiborder region of thin elastic sheet material extending around the entire periphery of this. intermediate "mass element. The additional diaphragm 50fis of'anoblong cone figuration and'its' thin elastic'region surrounding its center portion '52 is provided with two elongated slits 55 separating the elongated border edges 58 of the'diaphragm from'the'main inten mediate bodyvportion of the diaphragm. so'that the elongated intermediate main body portion of the diaphragm extending "between the two 51113555 may vibrate relatively tothe edge regions 56 and 5'! of the diaphragm 50.

In order togive the additional diaphragm 5d the required degree of stiiin'ess, its-"two end regions El and its twobcrderregions lifiare rendered substantially rigid so that they are restrained against elastic deformation by bending in the direction transverse to the diaphragm andbystretching'in the direction of elongated border-regions iifi.

In the arrangement shown in Figs. 1 to '3, the edge regions 55; 5 or" the diaphragmfifl are given the required rigidity and are restrained against deformation by holding themall' clamped between facing border regions of 'the two casing walls 2!, 2-2.

As'indicatedin Figs, 1,2A, and 5,the base Wall 22 is provided with a slightly raised border portion 25 of substantially the same thickness as the facing border region of the casing wall 2| to which it is clamped. The border portion 25 of the casing wall 22 has formed therein a recess 26 bounded by a flange 21, the recess 26 being just deep enough for receiving the edge elements 56, 5? of the diaphragm and to ensure that the entire edge region of the additional diaphragm 50 is held positively clamped and restrained against deformation when the two casing walls are flixed to each other in their assembled condition by the screws 23.

The clamping connection between the edge regions of the additional diaphragm 50 with the casing walls 2 l, 22, serves thus as the sole connection of the casing walls to the elastic portions of I the diaphragm 50 through which the inner Vibratory unit is resiliently carried in a vibratory condition in the interior of the casing structure.

The device of the invention shown in Figs. 1 to '7 is or about the same compact size as the standard bone receivers which are now on the market, the

height being increased only by about /32 of an inch, represented by the thickness of the addi- 'core structure are represented in the analog of Fig. 9 by voltage source V, and the electric voltage developed across the impedance Z represents the forces exerted by the contact wall on the bone structure. When a device of Fig. 8 is used as a throat microphone, a voltage applied across the terminals of element Z represents the forces exerted by the throat on the contact wall of the device of Fig. 8, and the voltage developed across element V represents the output of the microphone. 1

In Fig. 10, the full line curve H shows the fre- I quency response of a deviceof the invention, such as shown in Fig. 8, when used as a throat microphone under the action of constant velocity vibratory forces imparted to the contact wall casing by an artificial throat. The dash-line curve 12 of Fig. shows the corresponding response characteristic of a device having the same components as Fig. 8, but without the additional diaphragm 50; and with the center portion of the inner diaphragm 40 directly connected to a portion of the contact casing 2 I, 22, the peaked region l2l of the response curve licorresponding to the resonant frequency of such vibratory device. The del vice of the invention exhibits also similar marked superiority in performance when used as a bone receiver.

When a device of the type shown in Fig. 8, but

- without the additional diaphragm 50, is used as a contact microphone, such as a throat microphone,

and is subjected to constant velocity vibratory forces imparted to the contact casing, it will generate a voltage which rises with the frequency at the rate of about twelve decibels per octave, in the part of the frequency below the resonant frequency of the vibratory structure. Since the housing is not absolutely rigid, it introduces reso- Fig. 8 shows. diagrammatically the 9 nant peaks and dips at relatively high frequencies.

By providing such device with the additional diaphragm arrangement of the invention, its vibrating system is made to operate with two resonant frequencies in the manner indicated by curve H in Fig. 10, namely, the low resonant frequency indicated by peak 1 Il corresponding to the resonant peak 12-! of the device which does not have the additional diaphragm, and an additional resonant frequency in the high frequency range between about 3,000 and 4,000 cycles, indicated by peak 'H-2.

The two resonant frequencies with which the device operates depend on the magnitude of the masses L-I, L2 of the device and on the stiffness of its spring C-l, C-2. Since the additional diaphragm 50 supports the whole inner structure, it can be made very stiff so that the higher resonant frequency shall be in the range between about 3,000 and 4,000 cycles which is desirable for securing high intelligibility of speech when such a device is used as a throat microphone or a hearing aid bone receiver.

In a device of the type described, it is also desirable to suppress the peak in the response characteristic caused by the low resonant frequency of its vibrating system. According to the invention, this is accomplished in a very simple and effective manner by introducing damping means between the mass of the vibrating magnetic structure 30' and the contact casing, in a manner indicated diagrammatically in Fig. 8 by mechanical resistance element R. The corresponding electric analog of such device is shown inFig. 11. By introducing such damping resistance element between the vibrating magnet core structure 30 and the casing, the low frequency resonant peak I I-I of the response curve ll of such device may be suppressed and the response brought down to a level represented by the dash-dot curve portion ll-3, without reducing the effective cooperation of the elements in extending the frequency range of such devices.

The eifectiveness of the damping resistance R in the operation of an inertia-reaction device of the invention may be more fully explained by reference to the electric analog of such device shown in Fig. 11. In this analog, the mesh formed by the elements L-I, Cl and R rep resents the corresponding components of the device shown in Fig. 8 which determine the low resonant frequency of the system. This mesh is damped ver effectively by the serially included resistance R to a degree sufficient to suppress the low frequency peak of the response curve which has a detrimental effect on the intelligibility with which the device has to operatein order to be fully effective.

On the other hand, the mesh formed by elements C-l, L-2, 0-2 corresponds to the components of the device shown in Fig. 8 that determine the high frequency resonance of the system. The high frequency current in this mesh C-l, L2, C2 is only negligibly affected by the damping resistance R because only the voltage drop across the element C-l can contribute to a current with a resistance loss in the mesh C-l, L-l, R and this current is very small because the inductance L-l corresponding to the large mass of the device represents a high impedance for. high frequency currents.

An electromagnetic energy translating system of the invention of the type represented by the electric analogs of Figs. 9 and 10, operates as a band-pass filter which has a given response in 1 part of it.

translating energy over the frequency band in the region between :the 1 two resonant frequency peaks ll-I, Tl2 'of curve -'H (Fig. '10), .the transmission of the energy being substantially cut off below and above this'frequency band.

vThe frequency of the vlower 'limit 'of ithe frequency band, corresponding "to the 'lowenpeak -Hl, isdetermined by the magnitude of the mass L-! andofthestiffness C-I of anienergy translating device of the type shown rdiagrammatically-in-Fig'ii. The upper limit lofuthe frequency band corresponding to the resonant frequency peak 'H- 2 is approximatelydetermined by the-magnitudexof the elements L2,'C--l and C-2 of the-energy-translating .unitrof'the type shown in :Fig. 8.

:By suitably proportioning'and varying theratios'of Lie-I, L'2, -C|, C-'-2, the band Width over which such' energy:translating'device has'a good frequency response andits'cutoff -.frequenn 'cies,'can be 'chosen in proportion to meet any special requirements. Thus, an energy translating device of the type shown has-proved very effective for determining the null'point of a bridge system used to locate mines which-used an ensistan'ce interconnected between the casing'structureand the vibrating magnet structure flk FA shell M, of thin sheet metal, such as brass'for instance, is=placed around the magnet'structure so that the walls of the 811611174 -shall=be separated from the outer surfaces of the=magnet core structure '30 :byagap region 15. The shell iltzis afiixed to the casing wall structure-2i, "22"by"proviolingthe lower edges with flange portions Tl,

shaped to fit over the'end regions "51 of the additional diaphragm '50 and be rigidly clamped therewith between the two wall members 21,322 'of the casing'structure, in themanner indicated in-Figs.-1 and 2. Theshell M forms thus an extension of the casing wall-structure and a fixed In the gap region between the shell 14 and the exterior-surface of the magneticcore structure.- arerplaced stripvportions E8 of yieldable damping material, such-as a very soft grade -'oi,.-.

rubbery clamping-material, so'that the relative vibratory motion between 'the magnet structure 30 and the shell 14 surrounding it shall be damped -for suppressing the low resonant peak 1 l--l, in the manner-indicatedin Fig. 10. v

A strip -of damping material =18 may. be cplaced .in theigap 15 around the entire periphery of the yoke member r3l :so that the *relative vibratory :motion between the magnet'structure'ilfi emclthe or'both surfacesof the clampingfstrip "'Fd' m'ay be partially coated with :a cement so. as to cement surface portions of the damping rstrip *1 8"either -to =theshel1 ortotheyokefi I or to both.

A-shell iarrangement aof the typel-shown makes it possibletoiequip the lint'ernal vibrating Tistru'crture with a damping element through which :its vibrating :magnet core structure -is connected to a rigid ,zpart 20f @the 'casing structure before the internal kvib'rating :unit is 'mountedziniands afiixed in itsoperativelposition :within its contact casing structure.

In Figs. r13 to 17 l is shown another form of san 'inertiareactionaenergy translating :device .of the invention specifically designed-forfluseaasaa throat :microphon'e. It has an internaL electromagnetic vibrating structure including a magnetic wcore structure 30-*and-:an' armature diaphragm-40 simi- :lar to the corresponding elements of the device described in'connection with Figs. .-1-to 7. The armature; portion 4'2' of the 1 electric vibrating :unit .is joined *across :the spacer Fma'ss a member :54 to v the contact wall: structure of :the-acasing throug'h aniadditionat vibratory diaphragm memberz50-"l as in 'theldevice of. Figs. 1 ntO' 7.

The additional :rdiaphragm ill-4|, *ewhich is shown in :plan :view in Fig. :14, .-is provided "with two: elongated slits -55l separating its :central vibratory region zfrom its I elongated aedgewegions 56l. The entire edge region tofithethinrdia- :phragmr50--'l is given igreat rigidity1by uniting .to one tor both :of its sides, asrby soldering -or welding, two reinforcing frame ;.members :81, .1 in the 'manner;shown in Figs. 13, 15, so that lonl the intermediatezportion :oftthe diaphragm 350-4 extending between the "two slits 55'l 3 serves as a vibrating part of the diaphragm.

ZIheinternal "vibrating structure so formed is mounted in :a central compartment of :a casing structure formedzof :two casing :wallzmembers :82, -33 of ;generally circular. shape "which are afiixed '.t0'*each:other by twoxscrews 84,585. The-:two'cas- I ing wall .amemb'ers 82, "83 have facing wall .se'ctiOllsliB'fi/KT arranged soas :to: clampinglyiengage the rigid-edge region of the additional diaphragm :50-1 *with itstwo reinforcing frame members'siil and hold the internal vibrating 'unit :30, 40 linaa vibratory condition :within the central compartment of :'the :casing structur'e.

Casing wall memb ere 83' hasi'formed in the border walliregionsadjoining athe compartment Wall section 81 an additional cavity 88 within which is aretained an enlarged bead member 0-] ef a junctionl'strap 2-92 ijoiningftwo similar microphone units in :the manner 'indi'catedin- EigJ-H. "The junction strap?!) 2 1maybe flexible, rubber lik'e ma- "terial and has embedded therein -electric 'E-c'ord :leads 283-], 293-42, 93-3 through which the operating "coils #of the it'wo microphones are Einterconnectedlto extern'al operating circuits. Each ahead .91 01stheiconnectingstrap 9 2 is provided mm iterm'inal :elemen'ts through which, the terminal ends of the ':-leads @93-1 ,f293-'-2, 93-'-3 are connected to the terminal ends of "the operating coil of :the respective emicrophone.

Asshown :in Fig. -1 3,ea"ch bead m'ember 'QI ris held :afilxed within .its'icavity space by the' clanip- :ing screw 'of the :casing, the ;clamping-;screw extending through an aperture formed in 'ithe -be'ad member =9l. The-othervclampin'g screw 84 of -;thetwo casing walls 82, 83 serves "in a' similar mannerto hold clampe'diibetween the two walls "theend: Ofil'flv connector strip 94,: of: metal; for :instance, WhiChziS provided with "afmale'ffastener projection -95 "for Ffastening E thereto the female fastener element: Oftfir flexible elastic strap 196' with which -a:-.double tmicrophone unit such as :shown in FigpFlW is retained on the ;neckof the speaker so-that the vibration transmitting-parts "of *the contact casings of the two microphones shall be held coupled to the Vibrating parts of the throat.

The inertia-reaction device of Figs. 13 to 17 is likewise provided with damping means inter-' connected between the vibrating inner magnet core structure 30 and the contact wall casing structure for damping and suppressing the vibrations within the frequency range of the low frequency resonant peak of such device.

The damping means of the device shown in Figs. 13 to 17 has a shell IOI, such as shown in Fig. 18, which is placed around the magnet structure 30 and is provided along its lower edges with flange portions I02 shaped to fit over the edge regions of the additional diaphragm 50-I with its reinforcing frame members so that shell flange I02 may be rigidly clamped with the diaphragm edges between the facing portions 86, 8'! of the casing wall structure for holding the shell IOI fixed as part of the casing wall structure.

As shown in the enlarged detail Fig. 19, the shell I M extends upwardly above the level of the magnet core 30 and is provided with a top wall member I04 overlying the yoke member and separated therefrom by a gap space I05. The upward portion of the shell structure I0! is provided along one side thereof with a window-like opening I06 and a transverse slot I01 extending from'the opening I06 to the central region ofthe top wall I04 so that a damping unit I II may be inserted through the shell opening I06 and interconnected between the upper surface of the magnet structure 30 and the top wall I04 of the shell NH. The damping unit III is made in the form of a fiat container of thin flexible, soft synthetic resin film material which is shaped to fit into the gap space I between the; upper" shell Iwall I04 and the yoke" plate 30. The plate-member II3 extends across the interior space of the con-"a 40 mounting shank II4 extending through an opening in a thickened spacer wall portion II5 of the tainer III and is provided with a threaded container I II and a hole in the upper shell wall I04 so that damper plate H3 may be affixed in spaced relation to the upper shell wall I04 as by a nut I I6 engaging the threaded shank I I4. The interior space II 2 of the container III is filled. with a damping fluid or liquid and a plate member H3 is held immersed in the liquid filling the container space IIZ, so that a relative vibratory motion between the liquid in the container II I and the damper plate II 3 shall produce a substantially pure-resistance damping effect.

The damper plate II3 with its shank may be placed in the interior of the container either through the wall hole in the spacer portion H5, particularly if the container is made of rubberlike material, such as synthetic rubber or alternatively, the damper plate my be inserted through a slit in a side wall of the container which is sealed thereafter, as by an application of a cement to the border portions of the slit. 'The eifect. The shank II4 is arranged to fit tightly within the hole of the container I I I and its spacer portion II! for assuring that when the damper unit is aflixed in its position to the upper shellwall I04 the liquid in the container is tightly sealed therein. By providing the shell IOI with a side wall opening [00 and a slot I01, the damp-' ing unit may be mounted in its place after the shell is first positioned on the edge of the additional diaphragm, and afiixed thereto, if desired.

Alternatively, the shellvHlI is merely providedwith an opening in the top wall I04, in which case the damping unit MI is first afiixedin its operative position against the inner side of the top wall I04 by inserting the shank H4 through the top wallopening and clamping it with the nut I I6.

Fig. 20 isan enlarged detail view similar to. Fig. 19 of a modified form of damper arrangement forsuch device. A shell I20 similar to the shell of Fig. 18 isv provided with a top wall I2I having forme-dtherein an opening bordered by an".

edge region I22 which is engaged by overlapping borderregions I23 of a damper element I25 which is held aifixed to the vibrating inner magnet structure as by a screw I26 engaging-a threaded hole formed inothe'facing pole piece-portion of.

the'magnetic core structure 30.

The damper element I25 is made of a mate-w rial which produces a damping resistance effect when it is vibrated under-the action of the vibratory motionof the inner magnetic structure -30 relativel to the border portions I22 of the shell wall I2 I. The damper element 1 25-may be formed of a plurality of superposed thin sheet elements.

of paper or fabric having pockets of air entrapped between the adjacent superposed sheet elements so that a vibratory motion imparted to the sheet elements causes the entrapped air to be subjected i to a frictional motion relative to/the sheet -ele- 1 m t V I I Alternatively, the angry e em nt at i;

I made; of; a synthetic I resin material, such as Wis-" 1 coloid; which is soft andmyieldable and which has entrapped-therein air pockets so that when the magnetic structure 30 vibrates relatively to the shell wall I2I the corresponding vibratory motion imparted to the damper element I25 will .cause it to act as a damping resistance. t

In accordance with the invention, a shell such as the shell Mil shown in Fig. 18 forming part of the damping structure; is affixed'to the edge region of the additional diaphragm before the internal vibrating unit is affixed in its posi+ tion within the casing; and one of the end walls of the shell is provided with a-terminal block I33 having mounted thereon exposed electrically con- 1 ducting terminalelements I32 to which the ends of the coil:windings 33 of the device are con: nected; and the exposed terminal elements I32 are arranged so as to be either directly engaged by th contact plugs of a cord plug through which the coil is connected to externalcircuits, orthe exposed terminals I32 are arranged to automaticallyestablish electric connections with the terminal elements mounted in the facing held in the facing wall portions of the enclosing cas ing and arranged so that when the casing is .placed over the shell the terminal elements of the casing automatically establish electric connections with the terminals I32 of the shell; the terminal elements of the casing being arranged for detachable connection with the cord plugs of a cord through which the device is connected to external circuits.

It will be apparent to those skilled inthe art that the novel principles of the invention disclosed herein in connection with specific exem plifications thereof will suggest various other;

niodifications and applicationsofithe same. Itgie i. An;- ener y; trans-l'ating devioe-s as; by;

aqcordingly desired= that? in construing the claim-I inuwhichithe contactportiomformsiparti breadth of 'the appended-"claims they shall not of a; casing-structure enclosing: the diaphragm be: limited to the specifieexemplifications ofzthe memberpandflhe; elements-f the-.magneticaoore invention, described above. structura, said devices having damping: meansi Ieolaims including a damping resistance element. coneli In an electromechanicalenergy-translating; ated? between:amelementzof: the vibratory/cone device adapt'ed-tp be held coupled t tacti portion and". an] element of the additional bratoryr body a vibratory contactportion adapted mass por ion-so asv o d mm P Trm tiO I torbe-heldcoupled to the body;av b atory dia- 10% fgisa-idiadditional mass portionzrelatively:to-z said phragmvmember having an intermediate, mass" n fi i rfii m pQlfiion:resiliently'joinedto said contact portion GiAm energy; translating d vi e as-zdefined by? so". as to be carried thereby in a vibratory--con- Claim; ill-whichthecontactpo o fo s-D t" dition; anadditional massportion larger than ofi a easing; structure, enclosing the; diaphragm theintermediatemass portionand; resilient junc memberand! thelel'ements of the masnetiov re tion. elements through which it is connec-ted to structure, saidtdev cei avin damp ng means inn said" intermediate massportion so that the ad*- lcludingra' dampin esistance element connect'ect. dit-ional massportion is resiliently carried: in a. fitweenian element: of the ivibratorp contactlpor vibratory condition by" said intermediat mass; tionwandan' elem-entaofitheadditionalmassportiom porton; said-additional mass portion and said sozaszto-damp thevibratory motionrof'said' ad=-. intermediate massportion forming parts of" a ditiona'l mass portionzrelativelyl to said' contact magnet-i9 core structure eparated; by a, gap portion andlinc whichrth-eaadditina'l mass portion across which they-vibrate windings interlinked is; of? a; larger-mass: thana the intermediate mass: with said core structure so that a: relative=vibra portion: tory;motiorrbetween-the-additional and theinter- 7'..An: energy translating deviceiashclaimedinmediate massportion acrosssaid gap: produce claim I. in .whichi the=-contactiportion fOrmSl part corresponding volta-ges'in'said windings and that; f" a" casing' Structurev enclosing the diaphragm oscillatory; currents impressed on saidwindings member: and the elements of the magnetic core produce correspondingwibratory motion between structure-5 saiddiaphragm member being; or: said mass portionsacross said: gap; said (1131? obltmgshapeand two soft opposite-edge regions phragnr member including an elasticregion of of said diaphragm memberext'endinggenerallythin elastic sheet material extending between parallel: to its-longer sides, the opposite sides-oh the-peripheryofjsaid intermediatemass portion its:-. intermediate masss. portion being separated and? the; border; region of said diaphragm memtherefrom byelongated, slitsfi so. that the inter berg; said-1 diaphragm; member being formed of 3,5 mediate mass. portion, may" vibrate relativelywo an elastic sheet memberall elements; or whiclr, said; edge regionfit,

are. substa ntially confined to the pianeoe said? iAn energy translating;-devic-eraaclaimed.inz shee, member; andj-j a mass: portion joined-2 to a; claim-; 1,1 in; which the contmrti:portionv formsipart portion of said sheet-memberso as-to form-there:- of? a1 casing; structure' enclosing the diaphragm,

with said intermediate mass portion; the elastic- 40';- memberr and the elements: of themagnetic core region of said diaphragm memberbeing -bounded structure; said: diaphragmmember being of ob'-.. by--a continuous-edgeregion extending-alongthe long shape, and twolsofti opposite edge regions: border; region of said diaphragm member. and ofl' saidi diaphragm member extending generally: through whichsaid diaphragm membeniscon parallelztoits longer sides; the opposite sides of nected to said contact portion; the entire-con-- its, intermediate mass: portion beingseparatedf tinuous edge re i ni i diaphragm? mem r therefrom: by; elongated slits so thatithelint'erbeing held restrained against elastic deforma-M diat m ssportion. a ib ate relatively. to; tion' insubstantially all directions of its: sheetr aid: edge: regions; saiddevice having dampin r Structure? pp e e o -t e (line means; including a. damping resistance element: phraem eXtending n opposite sides 0 connected between anelement of the vibratory its intermediate mass portion being separated contactzportionand an element-ofthe additionalz therefrom y" l at d p s/1S0; that Said mass-.portion' soias'totdampithezvibratory motionintermed ate m s'p i n may vibraterelatively' of said additionarmass portion relativelyvto lsaid tolsaid two opposite edgeregions: contactpportion,

2: Anenergy translating-- device as -definedi'by- 5:, EMII. GREIBAC'H: claim; 1: in which the contact portion formspart;v of a casing: structure enclosingthe: diaphragm. REFERENGESGITED: gleqliggfiieund the elements of the magnetlccore The foil-lowing refenemes are. record, mime 3. An energy translating deviceas claimed inz o file patent claim 1, said diaphragm member being'ofobl'ona S:' =ATES:= PATENTS? shape, and two soft-opposite edge regions: of-=said Number Name, Date diaphragm member extending; generally parallel: 1. 1 6 H ht. tz l Nov to-its-longer sides, theopposite sid-eS'Of itSfin-teb 3 2 b 1926? mediatemass portion-being separated'therefrom' 1363020231 Reyno'lds May-243 927 by-elongated slits so that the intermediate:-masjs: 3 u Nov; 9 portionmayvibrate relatively to said: edge- 2;i 9;806' Lian et al Aug:15,-1939 2,202,906 Hawley June 4', 1940 4: An energy'translating'device as defined by 2252,3116 Giannimet a1 Aug claim lhaving damping meansinoluding adamp-- 23355250 Greibachr t, 9; 1941- ing resistance element connected between an 2353,099' Polk Sept. 12; 1944" element of thevibratory contact portion and anelement of the additional mass portion so-as- -to- FOREIGN BATENTS damp: the vibratory motion of said additional Number-- Country Date mass portion relatively tosaid contact-- portion; 10432291 Sweden-" v- Apr. 14; 1922 

